Apparatus for acceleration and application of negative ions and electrons

Abstract

An apparatus for generating X-rays from electron synchrotron radiation or beams of accelerated ions for ion radiography or ion therapy includes a source of electrons and a source of ions, both of which are connectable to preaccelerators. The preaccelerators supply the appropriate type of charged particle to a synchrotron accelerator which accelerates ions to an energy level that is appropriate for radiography or therapy and which accelerates electrons to a level that generates X-rays by synchrotron radiation in a useful frequency range. The accelerator system also includes a storage ring into which particles are switched and circulated for later use. Electrons are extracted from the synchrotron and injected into the storage ring by fast extraction using a kicker magnet and a septum magnet. They then circulate in the storage ring for periods of hours generating X-rays which may be used for lithography of computer chips with submicron resolution. The energy loss because of this radiation is continuously replaced by a radio-frequency acceleration system. During the period that electrons are circulating in the storage ring, the synchrotron may be utilized to accelerate ions for ion radiography or ion therapy with beam extracted from the synchrotron by stripping extraction through thin foils. Other simultaneous uses for the ions or electrons from the preaccelerator may prove advantageous.

What is claimed is: 
     
       1. An accelerator comprising an electron source, an electron preaccelerator connected to the source to produce preaccelerated electrons, means for accelerating the preaccelerated electrons to a final desired energy, and means for storing high current electron beams for long periods of time, the means for storing including a storage ring containing a nonevaporable getter strip disposed to form a distributed vacuum pump to achieve high pumping speed and very high vacuum and also to produce clearing fields to remove positive ions created by collisions of the electrons with residual gas inside the accelerator. 
     
     
       2. The apparatus of claim 1 wherein the means for accelerating comprises a synchrotron used to accelerate the preaccelerated electrons to a final desired energy, the synchrotron also including nonevaporable getter strips for the dual purposes of high speed vacuum pumping and producing clearing fields to remove positive ions. 
     
     
       3. An apparatus for producing accelerated positive ions comprising a source of negative ions, a preaccelerator receiving and accelerating the negative ions, a synchrotron connected to the preaccelerator to accelerate the negative ions to a predetermined energy at a high repetition rate, means for extracting the negative ions using a bump magnet and a septum magnet, a stretcher ring receiving and circulating the accelerated negative ions, means for stripping the negative ions to positive ions to extract them from the stretcher ring, and an ion station connected to one of the means for extracting the negative ions and to the means for stripping the negative ions to utilize the extracted ions. 
     
     
       4. The apparatus of claim 3 wherein the ion station comprises a medical therapy work station. 
     
     
       5. The apparatus of claim 3 wherein the ion station comprises a radiography work station. 
     
     
       6. The apparatus of claim 3 wherein the ion station comprises a medical imaging work station. 
     
     
       7. An apparatus comprising a source of negative ions, a preaccelerator receiving and preaccelerating the negative ions, a synchrotron accelerating the preaccelerated negative ions to a predetermined energy at a predetermined repetition rate, means for fast extraction of the negative ions from the synchrotron, means for injecting the extracted negative ions into an accumulator ring by charge exchange on each cycle of the synchrotron, and means for extracting the injected ions from the accumulator ring in a time period of the order of ten to fifteen seconds. 
     
     
       8. The apparatus of claim 7 comprising in addition a work station connected to the accumulator ring to receive accelerated particles from the accumulator ring and a bump magnet-septum magnet extraction system for extracting accelerated particles to the work station. 
     
     
       9. The apparatus of claim 8 wherein the work station connected tot he accumulator ring is a cancer therapy work station delivering a radiation fraction in a time interval of the order of ten to fifteen seconds. 
     
     
       10. The apparatus of claim 8 wherein the synchrotron is of lower energy than the peak energy of the accumulator ring, and wherein the accumulator ring includes means for accelerating accumulated beam in the accumulator ring from the synchrotron energy to a desired higher energy. 
     
     
       11. The apparatus of claim 9 comprising in addition means for charge-exchange extraction of ions from the synchrotron, and medical work stations connected to the synchrotron to receive and use the extracted ions. 
     
     
       12. The apparatus of claim 11 wherein the accumulator ring contains alternative injection systems and alternative extraction systems such that it can operate either as an accumulator ring or as a stretcher ring. 
     
     
       13. An apparatus comprising a source of negative ions, a preaccelerator receiving and preaccelerating the negative ions, a synchrotron accelerating the preaccelerated nagative ions to a predetermined energy at a predetermined repetition rate, means for extraction of the negative ions from the synchrotron by bump magnet and septum magnet, and a work station utilizing these negative ions. 
     
     
       14. An accelerator comprising a small diameter ring of short straight identical dipole and short straight identical quadrupole magnets for operation as a synchrotron, a storage ring of short straight identical dipole magnets and short straight identical quadrupole magnets, a source of negative ions and a plurality of window frame stripping foils disposed at each point of maximum amplitude of spatial oscillations of an accelerated beam, a plurality of dipole magnets, one each disposed with respect to a stripping foil, and a plurality of beam dumps disposed outside the accelerator such that errant beams strike a foil and are extracted into a localized beam dump without striking walls of the accelerator, thereby maintaining unusually low residual radioactivity. 
     
     
       15. The accelerator of claim 14 wherein the dipole magnets are C-shaped magnets, each having an opening on an outside circumference of the accelerator such that negative ions which are neutralized by residual gas in the accelerator and therefore exit the accelerator at any point in the circumference encounter a thin wall of a vacuum chamber of the accelerator with no iron beyond and therefore further reduce residual activity of the accelerator. 
     
     
       16. The accelerator of claim 14 comprising in addition means for moving the accelerated beam in a single selected turn with respect to one of the window frame stripping foils, and a plurality of detectors disposed outside the accelerator to detect extracted beam which has struck the stripping foil, thereby allowing a determination of the position of the circulating beam at any foil at any time without sophisticated diagnostics inside the accelerator. 
     
     
       17. An accelerator comprising a source of negative ions, an ion preaccelerator for preaccelerating the negative ions, a synchrotron, means for injecting the preaccelerated negative ions into the synchrotron for acceleration, means for injecting accelerated ions from the synchrotron into a storage ring, and a detector disposed outside one of the synchrotron and the storage ring to detect neutral atoms that have been neutralized by interaction with a residual gas in a vacuum chamber of the synchrotron or storage ring.